The present invention relates to a superconducting magnet and more particularly to an improved heat insulation support structure for a superconducting magnet.
A conventional heat insulation support structure for a superconducting magnet is shown in FIG. 1.
FIG. 1 shows in partial section a heat insulation support structure which is disclosed for example, in "A low heat leak support structural member for the superconducting Chicago Cyclotron Magnet" published in Advances in Cryogenic Engineering Vol. 27 (1982) pp 193-200, wherein a superconducting coil 1 is supported by a heat insulation support rod 5 against a room temperature wall of an insulation housing. The heat insulation support rod 5 is constructed of heat insulation support members 3a, 3b and a thermal anchor 4 inserted therebetween. A cooling pipe 4a is provided on the thermal anchor 4.
The heat insulation support members 3a, 3b and the thermal anchor 4 are thermally and mechanically connected to each other to form a heat insulation support rod 5, by means of which the superconducting coil 1 is supported against the room temperature wall 2 of an insulation housing 2a so as to be thermally insulated. Since the room temperature wall 2 is at a room temperature (300.degree. K.) and the superconducting coil 1 is at a cryogenic temperature (4.2.degree. K.), heat is transferred from the insulation housing to the superconducting coil 1 by way of the heat insulation support rod 5. In order to reduce this flow of heat, the heat insulation support members 3a, 3b are made of a material whose heat transfer coefficient is small, and the length L2 of these members is made as long as possible. Also, the flow of liquid nitrogen (whose temperature is at 78.degree. K.) through the cooling pipe 4a provided on the thermal anchor 4 further reduces the influent heat 91 to the superconducting coil 1.
FIG. 2 is a heat circuit diagram of the heat insulation support structure.
In the heat insulation support structure for the conventional superconducting magnet constructed above, it is necessary that the heat transfer coefficient of the heat insulation support members be lower and the length thereof be longer to minimize the influent heat to the superconducting coil. However, there are certain limitations in minimizing the influent heat due to the spatial distance between the normal temperature wall and the superconducting coil. As a result, in indirect cooling type superconducting magnets, the temperature of the superconducting coil rises due to the influent heat from the heat insulation support rod, thereby deteriorating the performance of the superconducting magnet.